[18a-PB01-1~25] 12.5 Organic and hybrid solar cells

▲ [18a-PB01-15] The modification of the electron transporting layer for decreased loss in open-circuit voltage in terms of tin perovskite solar cells

〇Liu Jiaqi¹, Liang Wang¹, Qing Shen¹, Shuzi Hayase¹ (1.The University of Electro-Communications)

Keywords:perovskite, electron transporting layer

The extensive utilization of solar energy is the target of researchers in energy, physics, chemistry, etc. Perovskite solar cells (PSCs) have been one of the most prevalent solar cells in the world due to their low cost and fast development in efficiency. Even though the efficiency of PSCs has reached around 25.7%, the toxicity of lead-based PSCs is fatal. Therefore, a new type of lead-free PSCs has been established by substituting lead with tin. The tin-based PSCs have extra advantages, such as smaller bandgap values and high charge-carrier mobility, compared to lead-based PSCs. So far, the efficiency of tin-based PSCs has reached 14.3%, which is still far from the theoretical prediction. The deficiencies are the unsatisfied incident photon-to-electron conversion efficiency (IPCE) and the loss in open-circuit voltage. C₆₀ has been widely used in the PSCs as an electron transporting layer (ETL). However, the open-circuit voltage seems to be a bottleneck that limits the overall efficiency. We investigated the band alignment between the hole transporting layer (HTL), perovskite, and ETL using the Kelvin probe and photoelectron yield spectroscopy. The proposed band alignment is illustrated in Figure 1. It shows that the band bending between perovskite and ETL is detrimental to electron transport due to the shallower Fermi level of perovskite than that of C₆₀. It also limits the open-circuit voltage of the device. Therefore, the modification on the ETL was done to decrease the loss in the open-circuit voltage.