Ion-modulated radical doping of spiro-OMeTAD for more efficient and stable perovskite solar cells

Abstract

Record power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have been obtained with the organic hole transporter 2,2′,7,7′-tetrakis( N , N -di- p -methoxyphenyl-amine)9,9′-spirobifluorene (spiro-OMeTAD). Conventional doping of spiro-OMeTAD with hygroscopic lithium salts and volatile 4- tert -butylpyridine is a time-consuming process and also leads to poor device stability. We developed a new doping strategy for spiro-OMeTAD that avoids post-oxidation by using stable organic radicals as the dopant and ionic salts as the doping modulator (referred to as ion-modulated radical doping). We achieved PCEs of >25% and much-improved device stability under harsh conditions. The radicals provide hole polarons that instantly increase the conductivity and work function (WF), and ionic salts further modulate the WF by affecting the energetics of the hole polarons. This organic semiconductor doping strategy, which decouples conductivity and WF tunability, could inspire further optimization in other optoelectronic devices.

24.20%‐Efficiency MA‐Free Perovskite Solar Cells Enabled by Siloxane Derivative Interface Engineering

“…The long‐term stability of FA 0.83 Cs 0.17 PbI 3 films and PSCs is investigated under different conditions. [ 42–45 ] As shown in Figure a, the fading rate of the optimized sample is significantly slowed down during the aging process in ambient air (RH ≈ 35–40%, T = 25 °C). According to the XRD tracking result of the perovskite films (Figure S10, Supporting Information), the diffraction intensity of (001) plane for the control perovskite film decreased faster than that of the optimized perovskite film, indicating that air stability of perovskite film is improved after PSiOH modification.…”

Spiro‐OMeTAD‐Based Hole Transport Layer Engineering toward Stable Perovskite Solar Cells

“…The optimized device was able to retain approximately 90% of the initial PCE after operation at MPP under 1 sunlight exposure for 1600 h. Recently, a new doping strategy for Spiro‐OMeTAD avoiding post‐oxidation was reported by Gao's group. [ 89 ] In their study, stable Spiro(TFSI − ) 2 radical was used as the dopant to increase the conductivity and affect energy levels of Spiro‐OMeTAD, whereas 4‐ tert ‐butyl‐1‐methylpyridinium bis(trifluoromethylsulfonyl)imide (TBMP + TFSI ‐ ), an ionic liquid salt, acted as the doping modulator to optimize the work function (Figure 7f). They further confirmed the role of ionic liquid salts by testing different types of ionic liquids.…”

“…g) J-V curves of different PSCs based on Spiro-OMeTAD HTL following the doping strategy. Reproduced with permission [89]. Copyright 2022, AAAS.…”

Fabrication and enhanced photoelectric properties of a novel Bi9O7.5S6/CdS composite film

“…7 There are two general strategies for promoting the development of solar cells: one is the exploration of new materials but it is always hard to predict their structures and photoelectric properties; 8 the other is the performance optimization of the known photoelectric materials. 9 As one of the extensively studied photoelectric materials, cadmium sulfide (CdS) has received great attention due to its excellent photoelectric response and can be utilized as building blocks for photovoltaic and optoelectronic devices. 10,11 Nevertheless, serious photocorrosion and insufficient light absorption can resist its further application in photoelectric devices.…”