In this work we demonstrate the planar configuration on hole conductor (HTM) free perovskite based solar cells. The CH 3 NH 3 PbI 3 perovskite was deposited using the spray technique to achieve micrometer size perovskite crystals. The number of spray passes changes the CH 3 NH 3 PbI 3 film thickness; for example, 10 spray passes achieved a film thickness of 3.4 μm of perovskite. Surprisingly, power conversion efficiency of 6.9% was demonstrated for this novel, simple solar cell structure with thick perovskite film that has no HTM. Capacitance−voltage measurements reveal charge accumulation at the CH 3 NH 3 PbI 3 /Au interface while the compact TiO 2 /CH 3 NH 3 PbI 3 junction showed a space charge region, which inhibits the recombination. Studying these interfaces is key to understanding the operation mechanism of this unique solar cell structure. This simple planar HTM free perovskite solar cell demonstrates the potential to make large-scale solar cells while maintaining a simple, low-cost architecture. ■ INTRODUCTIONOrganometal perovskite is a hybrid material composed of inorganic and organic components having high absorption coefficient, direct band gap, and high carrier mobility, 1−3 making it attractive for photovoltaic (PV) solar cells. In recent years, organometal perovskite has been used intensively in PV solar cells, achieving a power conversion of 20.1%. 4 Long electron−hole diffusion length was demonstrated in organometal perovskite which contributes to the high power conversion efficiency. 5,6 The perovskite based solar cells are not restricted to a specific solar cell configuration as might occur in other solar cell technologies. It has been demonstrated that perovskite, with and without the ability to inject electrons, functions on mesoporous metal oxide. 7−9 The perovskite can also be used both as a hole conductor (HTM) and as a light harvester due to the efficient hole and electron mobility, making the solar cell structure even simpler. HTM free cells show PV performance of 10−12% efficiency. 10−15 In addition, it is possible to observe efficient perovskite solar cells in planar architecture. In this solar cell structure, the perovskite is usually deposited on a planar substrate, contrary to the mesoporous configuration. One of the first reports on planar architecture discussed the evaporation of the organometal perovskite, achieving a uniform perovskite film with more than 15% efficiency. 16 Moreover, a vapor-assisted solution process was demonstrated as an efficient deposition technique for the planar structure, achieving 12.1% efficiency. 17 Flexible, low temperature planar perovskite solar cells were demonstrated on ZnO nanoparticles exceeding 10% efficiency 18 and on polymer substrate in an inverted configuration, where the perovskite was deposited between PDOT:PSS and PCBM. 19 Recently, inverted planar perovskite based solar cells where a CuSCN layer was deposited on the ITO surface showed 15.6% efficiency. The low interface contact resistance between the perovskite, the CuSCN, and the C60 ...

This paper presents for the first time Sb 2 S 3 -based solar cells operating on scaffold film. The scaffolds studied are Al 2 O 3 and ZrO 2 , for which no electron injection from the Sb 2 S 3 to the Al 2 O 3 or ZrO 2 is possible. As a result, one of the highest open circuit voltages (V oc ) of 0.712 V was observed for this solar cell configuration. Electron dispersive spectroscopy (EDS) was performed, revealing complete pore filling of the Sb 2 S 3 into the metal oxide pores (e.g., Al 2 O 3 or ZrO 2 ); the complete pore filling of the Sb 2 S 3 is responsible for the photovoltaic performance (PV) of this unique solar cell structure. In addition, intensity modulated photovoltage and photocurrent spectroscopy (IMVS and IMPS) were performed to extract the electron diffusion length. Electron diffusion length in the range of 900 nm to 290 nm (depending on the light intensity) was observed, which further supports the operation of metal oxide/Sb 2 S 3 solar cell configuration. Moreover, the Al 2 O 3 -based cells have longer electron diffusion length than the TiO 2 -based cells, supporting the higher open circuit voltage of the noninjected metal oxide-based cells. This work demonstrates the potential of Sb 2 S 3 to gain high voltage and to perform on a scaffold substrate without requiring electron injection.