Perovskite solar cells (PSCs) have achieved certified power conversion efficiency (PCE) over 25%. Though their high PCE can be achieved by optimizing absorber layer and device interfaces, the ...intrinsic instability of perovskite materials is still a key issue to be resolved. Mixed‐halide perovskites using multiple halogen constituents have been proved to improve robustness; however, the anion at the X site in the ABX3 formula is not limited to halogens. Other negative monovalent ions with similar properties to halogens, such as pseudo‐halogens, have the opportunity to form perovskites with ABX3 stoichiometry. Recently, thiocyanates and formates have been utilized to synthesize stable perovskite materials. This review presents the evolution of pseudo‐halide perovskite solar cells in the past few years. The intrinsic properties, their effects on crystal structure, and bandgap engineering of the pseudo‐halide perovskites are summarized. Various thiocyanate compounds applied in the fabrication of perovskite solar cells are discussed. The fabrication process, film formation mechanism, and crystallinity of pseudo‐halide perovskites are elucidated to understand their effects on the photovoltaic performance and device stability. Other applications of pseudo‐halide perovskites are summarized in the final section. Lastly, this review concludes with suggestions and outlooks for further research directions.
Monovalent pseudo‐halide anions share similar properties to halide anions. This review presents the evolution of pseudo‐halide perovskite solar cells in the past few years. The role of pseudo‐halides and their position and occupation in perovskite crystal, its impact on perovskite film quality, solar cell stability and photovoltaic performance, and pseudo‐halide optoelectronic devices beyond solar cells are compared comprehensively.
A new series of structurally simple and easily accessible hole‐transporting materials (HTMs) YZT1–YZT4 using porphyrin backbone is devised for high‐performance perovskite solar cells (PSCs) with and ...without the aid of doping. The YZT‐series HTMs have either push–push or push–pull type planar linear molecular geometry with substitution of linear or branched alkylamine. UV–vis absorption, photoluminance (PL) quenching experiments, and theoretical studies all suggest a different pattern of molecular packing induced by molecular geometry and/or substituted chains. Nonetheless, both types of porphyrin HTMs perform well in TiO2‐based PSCs when doped YZT4 with a power conversion efficiency (PCE) of 14.95% and undoped YZT1 with a PCE of 13.10%. The results clearly reveal the potential for porphyrin‐based HTMs for use in dopant‐free PSCs.
A new series of dopant‐free hole‐transporting materials (HTMs) YZT1–YZT4 featuring porphyrin backbone is achieved in which the best power conversion efficiency (PCE) of YZT4 is 14.95% for doped and that of YZT1 is 13.10% for dopant‐free perovskite solar cells (PSCs) based on TiO2 semiconductors.
The use of a pseudo-halide anion, such as thiocyanate (SCN–), as an additive in the composition-engineered perovskite film is verified and its impact on the perovskite solar cell (PSCs) performance ...is investigated. The perovskite precursor added with a small amount of formamidinium thiocyanate is deposited by a one-step solution process to prepare the perovskite film. We observe a significant enlargement in domain size after the incorporation of thiocyanate ions in the perovskite film. Moreover, a trace amount of thiocyanate groups across the perovskite film measured by the time-of-flight secondary ion mass spectrometer identifies the thiocyanate existing inside the perovskite bulk, especially near the film bottom. Replacement of halide with thiocyanate groups in the perovskite framework effectively suppresses bulk recombination in the perovskite film, leading to an improvement on the open-circuit voltage (V OC) and fill factor for the pseudo-halide-based PSCs. Our studies confirm the existence of SCN– in the final film and the passivation effect of SCN– for enhancing the device performance.
A new series of structurally simple and easily accessible hole‐transporting materials (HTMs) YZT1–YZT4 using porphyrin backbone is devised for high‐performance perovskite solar cells (PSCs) with and ...without the aid of doping. The YZT‐series HTMs have either push–push or push–pull type planar linear molecular geometry with substitution of linear or branched alkylamine. UV–vis absorption, photoluminance (PL) quenching experiments, and theoretical studies all suggest a different pattern of molecular packing induced by molecular geometry and/or substituted chains. Nonetheless, both types of porphyrin HTMs perform well in TiO
2
‐based PSCs when doped YZT4 with a power conversion efficiency (PCE) of 14.95% and undoped YZT1 with a PCE of 13.10%. The results clearly reveal the potential for porphyrin‐based HTMs for use in dopant‐free PSCs.
Role of Additive in Perovskite Solar Cells Chen, Peter; Huang, Kuo-Wei; Chiu, Yueh-Ya ...
2023 30th International Workshop on Active-Matrix Flatpanel Displays and Devices (AM-FPD),
2023-July-4
Conference Proceeding
The role of additives, including formamidinium thiocyanate (FASCN) and crown ether of 18-crown-6 (18C6), in the perovskite solar cell (PSCs) is investigated. In the first work, we observe a ...significant enlargement in the perovskite domain size after the incorporation of thiocyanate ions (SCN - ). Moreover, a trace amount of SCN - across the perovskite film measured by the time-of-flight secondary ion mass (ToF-SIMS) spectrometer identifies the SCN - existing inside the perovskite bulk, especially near the film bottom. Additive of FASCN effectively suppresses the bulk recombination in perovskite film, leading to an improvement on open-circuit voltage and fill factor for the PSCs. Our studies confirm the existence of SCN - in the final film and the passivation effect of SCN - for enhancing the device performance. In the second work, we add a crystallization controlling agent of 18C6 in the doctor-bladed perovskite film to improve its film quality. Liquid-phase scanning electron microscopy (L-SEM) is conducted to study the effects of 18C6 on the perovskite precursor and the doctor-bladed perovskite film. The L-SEM image of the pristine perovskite precursor reveals self-assembly of micelles, while the addition of 18C6 effectively suppresses the size of the perovskite-based micelles in the perovskite precursor. This effect results in uniform-sized micelles in the precursor and a reduced crystal growth rate to achieve a high-quality perovskite film with preferred crystallinity, an enhanced perovskite domain size, and a smooth surface. Addition of 18C6 significantly improves the power conversion efficiency of doctor-bladed PSCs.
