Search

Monolithic all-perovskite tandem photovoltaics promise to combine low-cost and high-efficiency solar energy harvesting with the advantages of all-thin-film technologies. To date, laboratory-scale all-perovskite tandem solar cells have only been fabricated using non-scalable fabrication techniques. In response, this work reports on laser-scribed all-perovskite tandem modules processed exclusively with scalable fabrication methods (blade coating and vacuum deposition), demonstrating power conversion efficiencies up to 19.1% (aperture area, 12.25 cm2; geometric fill factor, 94.7%) and stable power output. Compared to the performance of our spin-coated reference tandem solar cells (efficiency, 23.5%; area, 0.1 cm2), our prototypes demonstrate substantial advances in the technological readiness of all-perovskite tandem photovoltaics. By means of electroluminescence imaging and laser-beam-induced current mapping, we demonstrate the homogeneous current collection in both subcells over the entire module area, which explains low losses (rel) in open-circuit voltage and fill factor for our scalable modules.

Lanthanide-based upconversion (UC) allows harvesting sub-bandgap near-infrared photons in photovoltaics. In this work, we investigate UC in perovskite solar cells by implementing UC single crystal BaF2:Yb3+, Er3+ at the rear of the solar cell. Upon illumination with high-intensity sub-bandgap photons at 980 nm, the BaF2:Yb3+, Er3+ crystal emits upconverted photons in the spectral range between 520 and 700 nm. When tested under terrestrial sunlight representing one sun above the perovskite's bandgap and sub-bandgap illumination at 980 nm, upconverted photons contribute a 0.38 mA/cm2 enhancement in the short-circuit current density at lower intensity. The current enhancement scales non-linearly with the incident intensity of sub-bandgap illumination, and at higher intensity, 2.09 mA/cm2 enhancement in current was observed. Hence, our study shows that using a fluoride single crystal like BaF2:Yb3+, Er3+ for UC is a suitable method to extend the response of perovskite solar cells to near-infrared illumination at 980 nm with a subsequent enhancement in current for very high incident intensity.

Monolithic two-terminal (2T) perovskite/CuInSe$_2$ (CIS) tandem solar cells (TSCs) combine the promise of an efficient tandem photovoltaic (PV) technology with the simplicity of an all-thin-film device architecture that is compatible with flexible and lightweight PV. In this work, we present the first-ever 2T perovskite/CIS TSC with a power conversion efficiency (PCE) approaching 25% (23.5% certified, area 0.5 cm$^2$). The relatively planar surface profile and narrow band gap (∼1.03 eV) of our CIS bottom cell allow us to exploit the optoelectronic properties and photostability of a low-Br-containing perovskite top cell as revealed by advanced characterization techniques. Current matching was attained by proper tuning of the thickness and bandgap of the perovskite, along with the optimization of an antireflective coating for improved light in-coupling. Our study sets the baseline for fabricating efficient perovskite/CIS TSCs, paving the way for future developments that might push the efficiencies to over 30%.

Vacuum-assisted growth (VAG) control is one of the most promising methods for controlling nucleation and crystallization of printed and coated large area lead halide perovskite-based layers for optoelectronics. To coat or print homogeneous high-quality perovskite thin-films at high fabrication yield, real-time process monitoring of the VAG is pivotal. In response, a 2.1-megapixel multichannel photoluminescence (PL) and reflection imaging system is developed and employed for the simultaneous spatial in situ analysis of drying, nucleation, and crystal growth during VAG and subsequent thermal annealing of inkjet-printed and blade-coated perovskite thin-films. It is shown that the VAG process, for example, evacuation rate and time, affects the film formation and provide detailed insight into traced PL and reflection transients extracted from sub-second videos of each channel. Based on correlative analysis between the transients and, for example, perovskite ink composition, wet-film thickness, or evacuation time, key regions which influence crystal quality, film morphology, and are base for prediction of solar cell performance are identified.

Advancing inverted (p���i���n) perovskite solar cells (PSCs) is key to further enhance the power conversion efficiency (PCE) and stability of flexible and perovskite-based tandem photovoltaics. Yet, the presence of defects at grain boundaries and in particular interfacial recombination at the perovskite/electron transporting layer interface induce severe non-radiative recombination losses, limiting the open-circuit voltage (VOC) and fill factor (FF) of PSCs in this architecture. In this work, we introduce a dual passivation strategy using the long chain alkylammonium salt phenethylammonium chloride (PEACl) both as an additive and for surface treatment to simultaneously passivate the grain boundaries and the perovskite/C60 interface. Using [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) as a hole transporting layer and a methylammonium (MA)-free Cs0.18FA0.82PbI3 perovskite absorber with a bandgap of ���1.57 eV, prolonged charge carrier lifetime and an on average 63 meV enhanced internal quasi-Fermi level splitting are achieved upon dual passivation compared to reference p���i���n PSCs. Thereby, we achieve one of the highest PCEs for p���i���n PSCs of 22.7% (stabilized at 22.3%) by advancing simultaneously the VOC and FF up to 1.162 V and 83.2%, respectively. Using a variety of experimental techniques, we attribute the positive effects to the formation of a heterogeneous 2D Ruddlesden���Popper (PEA)2(Cs1���xFAx)n���1Pbn(I1���yCly)3n+1 phase at the grain boundaries and surface of the perovskite films. At the same time, the activation energy for ion migration is significantly increased, resulting in enhanced stability of the PSCs under light, humidity, and thermal stress. The presented dual passivation strategy highlights the importance of defect management both in the grain boundaries and the surface of the perovskite absorber layer using a proper passivation material to achieve both highly efficient and stable inverted p���i���n PSCs.

Low-cost solar cells based on solution-processed organic inorganic hybrid perovskites with high photovoltage are highly sought after, especially for their use in tandem cells or for driving electrochemical reactions. Towards this end, we herein present a single-step method for the preparation of regular planar heterojunction solar cells based on formamidinium lead tribromide (FAPbBr(3)), which is fabricated through an antisolvent-assisted crystallization process. This results in the formation of improved film quality of the perovskite layer in terms of uniformity, surface coverage, crystallinity,and light absorption. Devices fabricated using such films utilizing 2,2',7,7'-tetrakis-(N,N-p-dimethoxyphenylamino)-9.9'spirobifluorene (spiro-OMeTAD) as the hole-transport layer exhibits an open-circuit voltage (V,) of 1.32 V with a power conversion efficiency (PCE) close to 6%. The de-vice performance is much higher than when using devices based on the conventional one-,step process (i.e., without using an anti solvent), where a Vo, of 1.04 V and a PCE of 1.1 % are obtained. Moreover, the devices,show better reproducibility with very little hysteresis.

Encapsulates are, in general, the passive components of any photovoltaic device that provides the required shielding from the externally stimulated degradation. Here we provide comprehensive physical insight depicting a rather non-trivial active nature, in contrast to the supposedly passive, atomic layer deposition (ALD) grown Al2O3 encapsulate layer on the hybrid perovskite [(FA0.83MA0.17)0.95Cs0.05PbI2.5Br0.5] photovoltaic device having the configuration: glass/FTO/SnO2/perovskite/spiro-OMeTAD/Au/(±) Al2O3. By combining various electrical characterization techniques, our experimental observations indicate that the ALD chemistry produces considerable enhancement of the electronic conductivity of the spiro-OMeTAD hole transport medium (HTM), resulting in electronic modification of the perovskite/HTM interface. Subsequently, the modified interface provides better hole extraction and lesser ionic accumulation at the interface, resulting in a significant lowering of the burn-in decay and nearly unchanged charge transport parameters explicitly under the course of continuous operation. Unlike the unencapsulated device, the modified electronic structure in the Al2O3 coated device is essentially the principal reason for better performance stability. Data presented in this communication suggest that the ionic accumulation at the spiro-OMeTAD/perovskite interface triggers the device degradation in the uncoated devices, which is eventually followed by material degradation, which can be avoided by active encapsulation.

A perovskite sensitized solar cell (PSSC) comprising ethyl ammonium tri-lead iodide (CH 3 CH 2 NH 3 PbI 3 ) and solid polymer electrolyte have been successfully fabricated and reported in this paper. Perovskite was synthesized by direct deposition of equimolar CH 3 CH 2 NH 3 I and PbI 2 in dimethylformamide (DMF) solution. It was further characterized using various experimental tools like XRD, UV–visible, SEM and EDAX. The fabricated PSSC showed a short circuit current density (J sc ) = 1.16 mA/cm 2 , open circuit voltage (V oc ) = 0.70 V, fill factor (FF) = 0.67 and efficiency (ɳ) = 0.75% at one sun condition. Comparative data between PSSC and dye sensitized solar cell (DSSC) are also discussed in this paper.

Though perovskite solar cells (PSC) have reached high efficiency comparable to its counterparts, it is still striving towards finding a strong hold in terms of long-term stability. Several approaches have been made to prevent the degradation of PSC. Here, we present low-temperature ALD deposited Al2O3 as an effective encapsulant for PSC. The encapsulated devices improve with PCE reaching up to 19.4% post 300 cycles of Al2O3 deposition. In-situ QCM and FTIR measurements reveal that trimethylaluminum gets trapped inside the spiro-OMeTAD layer and is available for the subsequent dosage of H2O during nucleation regime. Here we unveil the fact that the ALD grown Al2O3 is not only surface limited, but the material penetrates the spiro-OMeTAD and enhances the hole transport property, improving the overall performance of encapsulated cells. Intermittent measurements indicate that encapsulated cells are stable, retaining 84% of its initial efficiency by the end of 300 days. Subsequently we elucidate that the device measurements under continuous illumination and with different bias conditions and atmosphere show that the ALD grown encapsulation prevents ingress of moisture and oxygen into the cells maintaining their stability.