Hole-Conductor-Free Mesoscopic TiO₂/CH₃NH₃PbI₃ Heterojunction Solar Cells Based on Anatase Nanosheets and Carbon Counter Electrodes

Abstract

A hole-conductor-free fully printable mesoscopic TiO2/CH3NH3PbI3 heterojunction solar cell was developed with TiO2 nanosheets containing high levels of exposed (001) facets. The solar cell embodiment employed a double layer of mesoporous TiO2 and ZrO2 as a scaffold infiltrated by perovskite as a light harvester. No hole conductor or Au reflector was employed. Instead, the back contact was simply a printable carbon layer. The perovskite was infiltrated from solution through the porous carbon layer. The high reactivity of (001) facets in TiO2 nanosheets improved the interfacial properties between the perovskite and the electron collector. As a result, photoelectric conversion efficiency of up to 10.64% was obtained with the hole-conductor-free fully printable mesoscopic TiO2/CH3NH3PbI3 heterojunction solar cell. The advantages of fully printable technology and the use of low-cost carbon-materials-based counter electrode and hole-conductor-free structure provide this design a promising prospect to approach low-cost photovoltaic devices.

Tunable hysteresis effect for perovskite solar cells

“…21,22 By optimizing the mesoporous scaffold and perovskite absorber, hysteresis-less devices have been obtained with TiO 2 as the electron transporting layer (ETL). 23,24 In this study, it was found that the type of hysteresis effect in printable mesoscopic PSCs was highly dependent on the interlayer of c-TiO 2 . Through controlling the deposition of cTiO 2 layer, we realized normal and inverted hysteresis effect for such printable mesoscopic PSCs.…”

Research Update: Large-area deposition, coating, printing, and processing techniques for the upscaling of perovskite solar cell technology

“…In fact, similarly to DSCs, it is mainly utilized for the deposition of the nanocrystalline scaffolds in the mesoporous PSC architectures at both the cell level and module level (since it enables patterned deposition of the unit cells 45 ). Arguably one of the most interesting developments regarding screen printing has been the development of fully printed PSCs utilizing a stack of mesoporous layers, 5,46,47 as shown in Figure 3(f). 48 A three-layer stack of 1 µm mesoporous TiO 2 ETL, a 2 µm mesoporous ZrO 2 spacer layer, and a 10 µm mesoporous carbon black/graphite top electrode were all screen printed over a conducting substrate covered by a thin compact layer of TiO 2 .…”

“…4 Recently, carbon pastes have been utilized instead of the top metal electrode which can also be printed over large areas. 5,6 Generally thin film solar cells use conductive glass or plastic films as substrate photo-electrodes. The required transparency limits the conductivity, generating problems in terms of series resistance when increasing device dimensions.…”

Research Update: Strategies for improving the stability of perovskite solar cells

“…60 The carbon cathode is inexpensive, is not prone to corrosion, and, interestingly, can act as hydrophobic moisture barrier additionally increasing the stability of a perovskite solar cell. [60][61][62][63][64] In some architectures, devices using the carbon cathode do not even require a selective p-type contact. [60][61][62]65,66 Most remarkable is a triple-layer structure composed of mesoporous TiO 2 and mesoporous ZrO 2 , which is then infiltrated with MAPbI 3 and contacted by a thick carbon layer.…”