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Recently, the power conversion efficiency (PCE) of organic solar cells (OSCs) has significantly progressed with a rapid increase from 10 to 19% due to state-of-the-art research on nonfullerene acceptor molecules and various device processing strategies. However, OSCs still exhibit significant open circuit voltage loss (Δ

A ternary organic solar cell composed of two fullerene-free acceptors and a coumarin donor attained appropriate nano-scale phase separation, achieving a PCE of 15.54%.

The power conversion efficiency of the ternary PSCs (16.32%) is higher than that for binary counterparts, i.e., 13.16% and 12.62% for P(DTB-BDD):DBTBT-IC and P(DTB-BDD):Y6, respectively.

The structural flexibility of organic semiconductors offers vast a search space, and many potential candidates (donor and acceptor) for organic solar cells (OSCs) are yet to be discovered. Machine learning is extensively used for material discovery but performs poorly on extrapolation tasks with small training data sets. Active learning techniques can guide experimentalists to extrapolate and find the most promising D:A combination in a significantly small number of experiments. This study uses an active learning technique with a predictive random forest model to iteratively find the most optimal D:A combinations in the search space using various acquisition functions. Active learning results with five different acquisition functions (MM, MEI, MLI, MU, and UCB) are compared. Results reveal that acquisition functions that combine exploitation and exploration (MEI, MLI, and UCB) perform far better than purely exploiting (MM) and purely exploring (MU) acquisition functions. Interestingly, the proposed model can overcome the bottleneck of extrapolating small training data sets and find most promising D:A combinations in relatively fewer experiments.

Binary OSCs with an efficiency as high as 15.17% are prepared using a new acceptor with a 3,5-bis(trifluoromethyl)phenyl as the N-substituent in a benzotriazole core and a donor polymer.

To improve the power conversion efficiency of single junction polymer solar cells (PSCs), we have used a ternary blend consisting of a low bandgap D–A conjugated polymer P and two acceptors, i.e., one nonfullerene, Cz-IC, and one fullerene, PC71BM.

The power conversion efficiency of PBDB-T:CF3-BDP-Cz is 13.07%, which is higher than that for PBDB-T:CF3-BDP-TPA, linked to the more appropriate nanoscale phase separation for exciton dissociation and charge transport.

Organic solar cells (OSC) have drawn tremendous interest because of their potential for low-cost solution processing and color tunability. OSCs with bulk-heterojunction structures offer an attractive pathway to efficiently utilize solar energy and have the potential to make transparent and flexible devices. The design of new materials and optimized device fabrications with visible light transparency make this technology attractive for various applications, including greenhouses, windows, building structures, etc. In this review, we highlight the developments of fullerene-free acceptors (FFA) for semitransparent OSCs (ST-OSC) and device architectures, including transparent electrodes giving special emphasis on the power conversion efficiency (PCE) and the average visible transparency (AVT).

We have achieved a power conversion efficiency of 16.44% for the ternary polymer solar cell using a wide bandgap copolymer and two non-fullerene acceptors.

In this review, current progress, opportunities, and challenges for ML in OSCs have been identified. Given the rapid advances in this field, impactful techniques that have been useful in extracting meaningful insights are discussed.

One of the major hurdles that are preventing organic solar cells (OSCs) from leading the efficiency chart is non-radiative voltage loss (ΔVNR). So far, however, not much effort is made to predict voltage losses and unravel the correlation of losses with electronic and structural descriptors. From the literature, we create a dataset consisting of 154 unique donor:acceptor combinations with reported ΔVNR. The dataset includes information about frontier molecular orbitals (FMO), optical bandgap (Eg), molecular descriptors, and molecular fingerprints. Four machine learning (ML) algorithms (random forest regressor, gradient boosting regressor, support vector regressor, and artificial neural network) are used to predict non-radiative voltage loss and the results obtained are compared on the basis of Pearson rs, root mean squared errors, and mean absolute percentage errors. Best results are obtained with gradient boosting regressor by using FMO + Eg + RDKit descriptors (Pearson r = 0.859) and FMO + Eg + MACCS fingerprints (Pearson r = 0.857). We have also applied these ML models by using only molecular descriptors and only molecular fingerprints and got impressive results (Pearson r = 0.78 and 0.726). These results indicate that ML models can be effectively used for the prediction of ΔVNR and virtual screening of promising donor:acceptor combinations with reduced ΔVNR.

A new wide-bandgap conjugated D-A polymer denoted as P106 with a medium acceptor dithieno [2,3-e;3'2'-g]isoindole-7,9 (8H) (DTID) unit and strong 2-dodecylbenzo[1,2-b:3,4-b':6,5-b"]trithiophene (3TB) donor units shows an optical bandgap of 2.04 and highest occupied molecular orbital energy level of -5.56 eV. P106 is used as the donor and two nonfullerene acceptors-medium bandgap DBTBT-IC and narrow band Y18-DMO-are used as acceptors for the construction of binary and ternary bulk heterojunction polymer solar cells. The optimized polymer solar cells based on P106 : DBTBT-IC and P106 : Y18-DMO exhibit power conversion efficiencies of 11.76 % and 14.07 %, respectively. The short-circuit current density (22.78 mA cm-2 ) for the P106 : Y18-DMO device is higher than that for P106 : DBTBT-IC (18.56 mA cm-2 ) one, which could be attributed to the more photon harvesting efficiency of the P106 : Y18-DMO active layer. In light of the high short-circuit current densities and fill factors for the Y18-DMO based device and the high value of open circuit voltage of the DBTBT-IC based device, ternary polymer solar cells are fabricated by using ternary active layer (P106 : DBTBT-IC : Y18-DMO) and achieve a power conversion efficiency of 16.49 % with low energy loss of 0.47 eV.

The stability, efficiency, and cost etc. of dye sensitized solar cell (DSSC) does not depend on materials only. As these properties are linked with the method of layer preparation and deposition, therefore fabrication methods are crucial for enhancing the performance of DSSC. In this paper, we demonstrate the process of TiO2 layer deposition by screen printing (SP) and doctor blade (DB) techniques, and the complete fabrication of DSSC. In addition, the preparation method of TiO2 paste which is compatible for SP and DB techniques is also described. PV performance of TiO2 layer printed by SP based DSSC is 6.72% which is better than 4.86% achieved by DB based DSSC. It is worth mentioning that power conversion efficiency (PCE) of cells was improved when a simple white paper is placed on the back surface of DSSCs during I-V characterization. Due to white paper, the incident light will be scattered or reflected again in the active area. This enhancement is remarkable, and it improves the PCE from 6.72% to 7.25% for SP and from 4.86% to 6.13% for DB technique based DSSC. We also calculated the series resistance (RS), saturation current (IS) and ideality factor (‘n’) for SP and DB technique based DSSC to understand the internal phenomena (charge transfer and recombination) and how these values influence the PV parameters. The transparency and colour effect of the SP and DB technique based DSSCs were explained by average visible transmittance (AVT), colour rendering index (CRI), and correlated colour temperature (CCT).

Perovskite solar cells (PeSCs) prepared with single crystals (SCs) ideally exhibit higher power conversion efficiencies (PCEs) because they possess a lower density of structural imperfection and superior charge transport. However, the density of the surface defects on the SCs is still very high, thereby inevitably affecting the device performance. Herein, perovskite single-crystal micro-plates were grown on a hole-transporting material, poly[bis(4-phenyl)(2,4,6-trimethylphenyl) amine], through a space-limited inverse temperature crystallization method. The surfaces of the as-prepared SCs were passivated using trioctylphosphine oxide (TOPO) during the device fabrication to alleviate the impact of surface defects. The PCE values are averagely improved from 11.90 ± 0.30% to 14.76 ± 0.65% after the surface passivation; the champion device even exhibits a PCE of 15.65%. The results from photoluminescence and hole-only devices reveal that TOPO treatments effectively reduce the number of surface defects on the single crystals, thereby improving the photovoltaic performance. The surface passivation also inhibits the hysteresis behavior due to the lower defect density. Finally, the TOPO treatment also improves the stability of the single-crystal PeSCs, presumably due to the hydrophobic long alkyl chains. Thus, this work provides an effective approach to achieving high efficiencies of single-crystal PeSCs.

In this work, we have reported two donor materials ONAF and SNAF that complement the widely used non‐fullerene acceptor ITIC, with the aim to develop non‐fullerene all small molecule organic bulk heterojunction solar cells (NF‐ASM‐OBHJSCs). Two small molecule donors A‐D‐D'‐D‐A architecture, namely ONAF and SNAF are synthesized and explored their ability to act as donor material along with the ITIC acceptor. Benzodithiophene (BDT) is used as central donor unit (dialkoxy‐BDT for ONAF and Dialkylthiophene‐BDT for SNAF) along with novel naphthodithiophene (NDT) terminal donor to improve light harvesting and charge conducting ability of the donor materials. N‐Butylrhodanine is employed as terminal acceptor to enhance the intramolecular charge transfer (ICT) and to place energy level of the donor materials. Both the small molecule donor materials have good thermal stability, broad and intense absorption displayed in the UV‐vis region with energy levels suitable for ITIC acceptor. NF‐ASM‐OBHJSCs are fabricated by using all small molecules (ONAF & SNAF) as donors and ITIC as acceptor. OBHJSCs based on SNAF displayed superior photovoltaic properties with power conversion efficiency (PCE) as 9.94 % (Jsc = 15.93 mA cm‐2, Voc = 0.96 V and FF = 0.65) compared to ONAF based devices with PCE as 7.48 % (Jsc = 14.93 mA cm‐2, Voc = 0.82 V and FF = 0.61). The substantial high PCE of SANF is attributed to the broad absorption, relatively well‐matched HOMO‐LUMO energy levels between SNAF – ITIC acceptor, better film morphology for efficient charge transport and exciton dissociation at donor/acceptor (D‐A) junction. The observed PCE is one of the best reported for the NDT‐BDT‐based all small molecule non‐fullerene OBHJSCs. Moreover, simplicity in the device fabrication procedures and low energy loss associated are added advantages with the SNAF based devices. We predict that the HOMO‐LUMO levels (CV) of D/A falling in this category, as in Figure S7, with further close energy levels will have implications on the efficiency of OBHJSCs.

Ternary polymer solar cells employing two polymers (P2, PTB7-Th) and one non-fullerene small molecule acceptor (Y6) were constructed using a conventional structure. The PTB7-Th, P2 and Y6 exhibit complementary absorption spectra therefore, the ternary blend consists of these three can maximize the photon harvesting efficiency which is advantageous to boost of short circuit current density of polymer solar cell. After the optimization of the weight ratios between the two donors and keeping constant the weight concentration of acceptor and following solvent vapor annealing in THF for 40 s, P2:PTB7-Th: Y6 (0.3:0.7:1.5) based polymer solar cells attained the power conversion efficiency of 15.46%, superior to that for polymer solar cells based on binary active layers i.e., P2:Y6 (12.62%) and PTB7-Th:Y6 (12.84%), respectively. The open-circuit voltage for the P2:PTB7-Th:Y6 is about 0.88 V which is in between the values for P2:Y6 (0.94 V) and PTB7-Th:Y6 (0.85 V), consistent with the different highest occupied molecular orbital energy level for P2 (−5.38 eV) and PTB7-Th (−5.27 eV). The enhancement in the short circuit current may be associated with the broader absorption profile of the ternary active layer relative to binary counterparts while the enhanced value of fill factor may be originated from the balanced charge transport, suppressed recombination, and faster charge extraction.

Three ([Pt]-DPP)n polymers PA, PB, and PC bearing cyanobiphenyl, alkyloxyphenyl, and triphenylene self-assembling groups were synthesized. The optical, electrochemical, photophysical, and solar cel...

In fullerene-free single-junction organic solar cells despite a small interfacial energy offset between the donor and acceptor materials efficient hole transfer occurs, resulting in power conversion efficiencies (PCE) >16%. Here, we demonstrate efficient organic solar cells by tuning of the electronic properties through simple structural modulation of coumarin-based electron donors. The OSCs with C2:BThIND-Cl:Y6 ternary blends exhibit a PCE of 13.54%, with an increased open circuit voltage (VOC) compared to the C1:BThIND-Cl:Y6-based devices (11.27%). Interestingly, an efficient charge transfer is revealed despite a reduced HOMO orbital offset of 0.02–0.04 eV between the C2 donor and BThIND-Cl and Y6 acceptors, resulting in a lower energy loss of 0.45 eV in ternary devices while still maintaining a maximum EQE of ∼80%@820 nm. The work demonstrates the importance of simple coumarin-based donors and their role in performance improvement for fullerene-free ternary OSCs by facilitating charge carrier transport with suppressed recombination.

A new non-fullerene small molecule acceptor (MPU6) containing a diketopyrrolopyrrole (DPP) acceptor unit as the core, connected to dicyanomethylene-3-ethylrhodanine end-capped units via thienylethynylselenophene bridges, has been designed and synthesized and its optical and electrochemical properties have been examined. MPU6 has been used as an acceptor along with a wide bandgap polymer (TDTBTA) as the donor for solution-processed bulk heterojunction polymer solar cells, thus resulting in a power conversion efficiency (PCE) of 13.14%, which is higher than that obtained when PC71BM is used as the acceptor (6.69%). The increase in PCE for the MPU6-based polymer solar cell is due to the increase in both VOC and JSC, while the FF is lower than that for PC71BM. In addition, PC71BM has been used as a second acceptor to form ternary PSCs, thus achieving a PCE of 15.60%, which is significantly higher than those for the binary counterparts. The increase in PCE for ternary PSCs may be linked to better charge transport and energy transfer, which leads to better utilization of excitons and also leads to the enhancement of JSC and FF.

The progress in Bulk Heterojunction-Polymer Solar Cells (BHJ-PSCs) has received much interest since the emergence of non-fullerene small molecule acceptors (NFSMAs), and power conversion efficiency (PCE) have reached up to 18%. In general, a mixer of conjugated polymer Donor and NFSM as Acceptor consists of the BHJ photoactive layer. Their optical bands and the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are of great importance to improve the resulting PSCs' efficiency and performance of the polymer solar cells. The HOMO and LUMO of Poly(4,6-bis(5-octylthiophen-2-yl)benzo[1,2-b:6,5-b':3,4-c'']terthiophene-2,8-diyl)-alt-(thiophen-2,5-diyl]-alt-(5,6-difluoro benzo[c][1,2,5]thiadiazol 4,7-diyl (denoted as P95) and NFSMAs ITIC-F, were measured using cyclic voltammetry(CV). Optical bandgap energy for each material's were calculated by UV–VIS absorbance spectra. Further charge transfer study was carried out by photoluminescence (PL) spectroscopy. It's results show that efficient electron transfer from P95 to ITIC-F and hole from ITIC-F to P95. On the basis of experimental outcomes these polymer materials can effectively produce viable organic solar cell (OSCs) devices.

In this work, nickel oxide nanoparticles (NiO NPs) have been synthesized through highly versatile and cost-efficient chemical precipitation process using polyvinylpyrrolidone (PVP) as a surfactant. The X-ray diffraction (XRD), UV–Visible (UV–Vis), Thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) techniques were employed to characterize the synthesized NiO NPs. The XRD pattern studies revealed that the NiO NPs have a face-centered cubic (FCC) structure and the mean crystallite size of about 7 nm. The optical band gap of 2.88 eV estimated from the tauc plot of thin film UV–vis absorption spectra. FTIR transmission spectra display a prominent band at ∼433 cm−1, which coincides with the bending vibration of Ni–O bond. The prepared NiO NPs retain the prodigious potential as a transparent electrode towards the solar photovoltaic (PV) cell.

The recent emergence of small acceptor molecules that are nonfullerene (NFSMAs) of A–DA′D–A type, particularly Y6, has accounted for the effective organic solar cells (OSCs). A new acceptor derivat...

Two new molecules having D–A–D configuration, symbolized as LCS01 and EP02, have been synthesized, characterized, and used for both fullerene- and non-fullerene-based organic solar cells (OSC). Bot...

Two D-A copolymers consisting of fused ring pyrrolo-dithieno-quinoxaline acceptors are synthesized with different donor units, i.e., benzodithiophene (BDT) with alkylthienyl (P134) and 2-ethylhexyloxy (P117) side chains. These copolymers are used as donors and a narrow bandgap acceptor Y6 to fabricate bulk heterojunction polymer solar cell devices. Owing to the strong electron-deficient fused ring pyrrolo-bithieno-quinoxaline and weak alkyl thienyl side chains in BDT, the polymer solar cells (PSCs) based on P134:Y6 attain the power conversion efficiency (PCE) of 15.42%, which is higher than the P117:Y6 counterpart (12.14%). The superior value of PCE for P134:Y6 can be associated with more well-adjusted charge transport, weak charge recombination, proficient exciton generation, and dissociation into free charge carriers and their subsequent charge collection owing to the dense π-π stacking distance and more considerable crystal coherence length for the P134:Y6 thin films. This investigation confirms the great potential of a strong acceptor-weak donor tactic for developing efficient D-A copolymers consists of quinoxaline acceptor for PSCs.

An efficient PSCs consisting of a ternary active layer containing a medium bandgap conjugated polymer P and two well-known non-fullerene acceptors i.e. ITIC-m and Y6 was fabricated. An overall Power Conversion Efficiency (PCE) of about 15.13% was achieved, with the optimized ternary active layer consisting of 20 wt% of ITIC-m in acceptors i.e. P:ITIC-m:Y6 (1:0.3:1.2). This value is higher than that for the binary counter parts i.e. 12.10% and 13.16% for P:ITIC-m (1:1.5 w:w) and P:Y6 (1:1.5 w:w). The higher short circuit current density of the ternary active layer PSCs is related to the broader absorption spectra as compared to the binary active layer analogs. The open circuit voltage of this ternary active layer-based PSC is in between the PSCs based on P:ITIC-m and P:Y6, which may be related with the Lowest Unoccupied Molecular Orbital (LUMO) energy levels of both the acceptor and which form the alloy between the two acceptors. The overlapping of the absorption band of Y6 with the photoluminescence of ITIC-m confirm the energy transfer from ITIC-m to Y6, leading to the improvement in short circuit current. The balanced charge transport, the reduced charge recombination and the fast charge extraction in the ternary blend lead to the higher value of FF. Thus, all these combined effects lead to the high value of PCE.

In recent years, tremendous growth has been seen for solution-processed bulk heterojunction solar cells (BHJSCs) using fullerene-free molecular acceptors. Herein, we report the synthesis, characterization of a coumarin-based organic semiconducting molecule C1, and its use in BHJSCs as an electron donor. The compound exhibited an absorption band at 472 nm in chloroform solution with an optical energy gap of 2.33 eV. The HOMO/LUMO energy levels of C1 were found to be ideal for use in BHJSCs. Using PC