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Tin oxide (SnO2) is broadly used as an electron transport layer (ETL) in organic solar cells (OSCs). However, there are many hydroxyl groups and the defects of oxygen vacancy on the surface of SnO2, resulting in charge recombination. Herein, an electrolyte 4‐(dimethyl(pyridin‐2‐yl) ammonio)butane‐1‐sulfonate (PAS) is doped into SnO2 films with an appropriate proportion to improve the performance of the inverted OSCs. The PAS can coordinate with the Sn atoms in SnO2 films to reduce the surface defects, resulting adjustable work function and increased electron conductivity. Meanwhile, the PAS doping can decrease the surface energy of SnO2 layer, forming vertical phase distribution of the active layer for better exciton dissociation and charge transport. The PM6:Y6 based inverted OSC with SnO2 ETL shows a power conversion efficiency (PCE) of 14.72%, while the device with PAS‐doped SnO2 ETL demonstrates greatly enhanced PCE of 16.37%. The device performance can be further improved by using PM6:BTP‐eC9 as active layer and a PCE of 17.12% can be achieved with PAS‐doped SnO2 ETL. Furthermore, PAS‐doped SnO2 can effectively enhance the device stability under continuous illumination. These findings demonstrate that exquisite regulation of SnO2 layer via a small electrolyte molecule coordination is a promising approach to achieve efficient and stable inverted OSCs. [ABSTRACT FROM AUTHOR]

A new two‐dimensional tetrathienyl‐TBDT (TBDT‐4T) was synthesized by employing palladium‐catalyzed C─H benzannulation between an iodobiaryl and 1,2‐dithienylacetylene. The stannylated TBDT‐4T was copolymerized with di(thiophenyl)difluorobenzothiadiazole (FBT) and fluorothienothiophene (FTT) monomers to yield PTBDT‐FBT and PTBDT‐FTT, which showed high decomposition temperatures (421 and 408°C) and deep‐lying HOMO levels (−5.80 and −5.84 eV). The inverted solar cell device using PTBDT‐FBT:PC71BM (1:1 in wt%) blend showed a power conversion efficiency (PCE) of 4.16%, while the device using PTBDT‐FTT:PC71BM (1:2 in wt%) blend showed a PCE of 3.98%. [ABSTRACT FROM AUTHOR]

A new PC61BM-based fullerene, [6,6]-phenyl-C61 butyric acid pentafluorophenyl ester (PC61BPF) is designed and synthesized. This new n-type material can replace PC61BM to form a P3HT:PC61BPF binary blend or serve as an additive to form a P3HT:PC61BM:PC61BPF ternary blend. Supramolecular attraction between the pentafluorophenyl group of PC61BPF and the C60 cores of PC61BPF/PC61BM can effectively suppress the PC61BPF/PC61BM materials from severe aggregation. By doping only 8.3 wt% PC61BPF, device PC61BPF651 exhibits a PCE of 3.88% and decreases slightly to 3.68% after heating for 25 h, preserving 95% of its original value. When PC61BP with non-fluorinated phenyl group is used to substitute PC61BPF, the stabilizing ability disappears completely. The efficiencies of PC61BP651 and PC61BP321 devices significantly decay to 0.44% and 0.11%, respectively, after 25 h isothermal heating. Most significantly, this strategy is demonstrated to be effective for a blend system incorporating a low band-gap polymer. By adding only 10 wt% PC61BPF, the PDTBCDTB:PC71BM-based device exhibits thermally stable morphology and device characteristics. These findings demonstrate that smart utilization of supramolecular interactions is an effective and practical strategy to control morphological evolution. [ABSTRACT FROM AUTHOR]

We have synthesized six p-type copolymers, CPDT- co- TPADCN, CPDT- co- TPADTA, CPDT- co- TPATCN, CPDT- co- DFADCN, CPDT- co- DFADTA, and CPDT- co- DFATCN, consisting of a cyclopenta[2,1- b:3,4- b′]dithiophene (CPDT) unit and an organic dye in an alternating arrangement. Triphenylamine (TPA) or difluorenylphenyl amine (DFA) units serve as the electron donors, whereas dicyanovinyl (DCN), 1,3-diethyl-2-thiobarbituric acid, or tricyanovinyl (TCN) units act as the electron acceptors in the dyes. The target polymers were prepared via Stille coupling, followed by postfunctionalization to introduce the electron acceptors to the side chains. Because of the strongest withdrawing ability of TCN acceptor to induce efficient intramolecular charge transfer, CPDT- co- TPATCN and CPDT- co- DFATCN exhibit the broader absorption spectra covering from 400 to 900 nm and the narrower optical band gaps of 1.34 eV. However, the CPDT- co- TPATCN:PC71BM and CPDT- co- DFATCN:PC71BM based solar cells showed the power conversion efficiencies (PCEs) of 0.22 and 0.31%, respectively, due to the inefficient exciton dissociation. The DFA-based polymers possess deeper-lying HOMO energy levels than the TPA-based polymer analogues, leading to the higher Voc values and better efficiencies. The device based on CPDT- co- DFADTA:PC71BM blend achieved the best PCE of 1.38% with a Voc of 0.7 V, a Jsc of 4.57 mA/cm2, and a fill factor of 0.43. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

The electrical and optical properties of the hole transport layer (HTL) are critical for organic and halide perovskite solar cell (OSC and PSC, respectively) performance. In this work, we studied the effect of Mg doping on CuCrO 2 (CCO) nanoparticles and their performance as HTLs in OSCs and PSCs. CCO and Mg doped CCO (Mg:CCO) nanoparticles were hydrothermally synthesized. The nanoparticles were characterized by various experimental techniques to study the effect of Mg doping on structural, chemical, morphological, optical, and electronic properties of CCO. We found that Mg doping increases work function and decreases particle size. We demonstrate CCO and Mg:CCO as efficient HTLs in a variety of OSCs, including the first demonstration of a non-fullerene acceptor bulk heterojunction, and CH 3 NH 3 PbI 3 PSCs. A small improvement of average short-circuit current density with Mg doping was found in all systems.

Benzene-based 1,1-dicyanomethylene-3-indanone (IC) derivatives have been widely utilized as the end-group to construct acceptor-donor-acceptor type nonfullerene acceptors (A-D-A type NFAs). The extension of the end-group conjugation of nonfullerene acceptors (NFAs) is a rational strategy to facilitate intermolecular stacking of the end-groups which are responsible for efficient electron transportation. A bicyclic benzothiophene-based end-group acceptor, 2-(3-oxo-2,3-dihydro-1 H -benzo[ b ]cyclopenta[ d ]thiophen-1-ylidene)malononitrile, denoted as α-BC was designed and synthesized. The Knoevenagel condensation of the unsymmetrical 1,3-diketo-precursor with one equivalent of malononitrile selectively reacts with the keto group attached at the α-position of the thiophene unit, leading to the isomerically pure benzothiophene-fused α-BC. The well-defined α-BC with extended conjugation was condensed with three different ladder-type diformylated donors to form three new A-D-A NFAs named BDCPDT-BC, DTCC-BC, and ITBC, respectively. The corresponding IC-based BDCPDT-IC, DTCC-IC, and ITIC model compounds were also synthesized for comparison. The incorporation of the electron-rich benzothiophene unit in the end-group upshifts the lowest unoccupied molecular orbital energy levels of the NFAs, which beneficially enlarges the V oc values. On the other hand, the benzothiophene unit in α-BC not also imparts an optical transition in the shorter wavelengths around 340-400 nm for a better light harvesting ability but also promotes the antiparallel π-π stacking of the end-groups for efficient electron transport. The organic photovoltaic cell devices using a PBDB-T polymer and BC-based NFAs all showed the improved V oc and J sc values. The BDCPDT-BC- and DTCC-BC-based devices exhibited a power conversion efficiency (PCE) of 10.82 and 10.74%, respectively, which outperformed the corresponding BDCPDT-IC-, and DTCC-IC-based devices (9.33 and 9.25%). More importantly, the ITBC-based device delivered the highest PCE of 12.07% with a J sc of 19.90 mA/cm 2 , a V oc of 0.94 V, and an fill factor of 64.51%, representing a 14% improvement relative to the traditional ITIC-based device (10.05%).

A formylated benzodi(cyclopentadithiophene) (BDCPDT) ladder-type structure with forced coplanarity is coupled with two 1,1-dicyanomethylene-3-indanone (IC) moieties via olefination to form a non-fullerene acceptor, BDCPDT-IC. The BDCPDT-IC, as an acceptor (A 1 ) with broad light-absorbing ability and excellent solution processability, is combined with a second PC 71 BM acceptor (A 2 ) and a medium band gap polymer, PBDB-T, as the donor (D) to form a ternary blend with gradient HOMO/LUMO energy alignments and panchromatic absorption. The device with the inverted architecture using the D:A 1 :A 2 ternary blend has achieved a highest efficiency of 9.79% with a superior J sc of 16.84 mA cm -2 .