Organic Solar Cell With Efficiency Over 20% and V_OC Exceeding 2.1 V Enabled by Tandem With All‐Inorganic Perovskite and Thermal Annealing‐Free Process

Abstract

Organic solar cells (OSCs) based on polymer donor and non-fullerene acceptor achieve power conversion efficiency (PCE) more than 19% but their poor absorption below 550 nm restricts the harvesting of high-energy photons. In contrast, wide bandgap all-inorganic perovskites limit the absorption of low-energy photons and cause serious below bandgap loss. Therefore, a 2-terminal (2T) monolithic perovskite/organic tandem solar cell (TSC) incorporating wide bandgap CsPbI 2 Br is demonstrated as front cell absorber and organic PM6:Y6 blend as rear cell absorber, to extend the absorption of OSCs into high-energy photon region. The perovskite sub-cell, featuring a sol-gel prepared ZnO/SnO 2 bilayer electron transporting layer, renders a high open-circuit voltage (V OC ). The V OC is further enhanced by employing thermal annealing (TA)-free process in the fabrication of rear sub-cell, demonstrating a record high V OC of 2.116 V. The TA-free Ag/PFN-Br interface in organic sub-cell facilitates charge transport and restrains nonradiative recombination. Consequently, a remarkable PCE of 20.6% is achieved in monolithic 2T-TSCs configuration, which is higher than that of both reported single junction and tandem OSCs, demonstrating that tandem with wide bandgap all-inorganic perovskite is a promising strategy to improve the efficiency of OSCs.

Recent Advances in Wide-Bandgap Organic–Inorganic Halide Perovskite Solar Cells and Tandem Application

“…Except from organic-inorganic halide perovskites, allinorganic perovskites like CsPbI 3 , CsPbI 2 Br and CsPbBr 3 have also attracted extensive attention due to their excellent thermal stability and the potential for tandem applications [112][113][114][115][116]. The bandgap of CsPbI 3 perovskite ranges from 1.68 to 1.73 eV depending on the degree of PbI 6 octahedral tilting.…”

Inorganic CsPbI2Br halide perovskites: from fundamentals to solar cell optimizations

“…By optimizing the CsPbI 2 Br front cell, as discussed above, we believe that monolithic tandem CsPbI 2 Br PSCs can provide higher device performance with superior stability. In 2021 and 2022, the bottom cell derived from low E g organic semiconductors of PM6:Y6-BO, 120 PM6:Y6, 121,122 and D18:Y6 122 blend films have delivered a PCE of >20%. Meanwhile, it should be noted that the idea of a ‘tandem cell’ is an important direction to further enhance all types of solar cell performance to surpass the S–Q limit of 31–33% for single-junction solar cells.…”

Influence of Component Properties on the Photovoltaic Performance of Monolithic Perovskite/Organic Tandem Solar Cells: Sub‐Cell, Interconnecting Layer, and Photovoltaic Parameters

“…[50] Thus, the organic/ZnO interface must be modified to suppress the nonradiative recombination of the carriers. However, only a few studies have focused on the modification of the organic/ZnO interface, [19,51] and the highest reported efficiency of ZnO-based n-i-p SOSCs (PM6:Y6, V OC = 0.83 V, PCE = 16.08%) is still lower than that of the MoO x -based p-i-n SOSCs (PM6:Y6, V OC = 0.87 V, PCE = 17.5%). [41] Consequently, the exploration of high-performance n-i-p SOSCs is a valuable strategy for optimizing n-i-p POTSCs.…”

“…For both n-i-p POTSCs and p-i-n POTSCs, the nonoverlapped EQE spectra of the WPSCs are similar to the corresponding EQE of the single-junction WPSCs (yellow color in Figure 8), indicating fully exploited current in the perovskite sub-cells. [42,51,71,72] In contrast, the single-junction SOSCs suffer from significant EQE loss after being integrated into the POTSCs (blue color in Figure 8), resulting in lower J SC values. The loss for n-i-p POTSCs (Figure 8d-h) is even more severe than that for p-i-n POTSCs (Figure 8a-c).…”

“…The compromised EQE intensity of SOSCs in the tandem device indicates that compared with the WPSCs performance, the SOSCs performance is more sensitive to the device structure. Considering the high EQE intensity of the single-junction n-i-p SOSCs, [50,51,73,74] the use of metal-oxide ETL (ZnO) is not the main reason for the EQE loss in n-i-p POTSCs. In other words, the mechanism for the EQE loss of the organic sub-cells in POTSCs is attributed to the ICLs modulated carrier transport/recombination properties of the tandem devices.…”