Unveiling the Role of the Metal Oxide/Sn Perovskite Interface Leading to Low Efficiency of Sn-Perovskite Solar Cells but Providing High Thermoelectric Properties

Abstract

Tin halide perovskites (THPs) have appealing optoelectronic properties similar to lead halide perovskites (LHPs). However, THPs coated on metal oxide electrodes in normal-structure perovskite solar cells exhibit poor diode rectification, resulting in poor efficiency. This poor photoelectric performance in n–i–p-based THP solar cells is in contrast with LHP solar cells. We report that this deficient performance of THP solar cells is triggered by the defect states of the metal oxide layer. The defect states of the metal oxide can trap the electrons from the THP, leading to the prompt formation of Sn­(IV), which will increase the carrier density and lead to poor photoelectric performance. This observation was supported by the ultraviolet-photoelectron spectroscopic measurements of inorganic thin films Al2O3, SnO2, TiO2, ZnO, and ZrO2. However, this self-doping phenomenon resulting in the increase in carrier density can be applied to thermoelectric studies. Using CsSnI3/ZrO2 nanocomposites as thermoelectric active layers, we report a power factor of 186.58 μW/mK2 measured at room temperature, which is better than the 148.61 μW/mK2 of the original CsSnI3 thin film.

Enabling water-free PEDOT as hole selective layer in lead-free tin perovskite solar cells

“…To a similar conclusion arrived Baranwal et al measuring the conductivity of tin perovskite thin films growth on top of other metal oxides and attributing to Al 2 O 3 the least oxidising activity. 28 The control over the morphology of the perovskite films has been the most critical strategy for improving the PCE of perovskite PV. 29 Based on the films studied in this work, we expected to observe a strong correlation between the solar cells' morphology and PV performances.…”

“…To a similar conclusion arrived Baranwal et al measuring the conductivity of tin perovskite thin films growth on top of other metal oxides and attributing to Al 2 O 3 the least oxidising activity. 28 …”

Strategic Doping in Metal Halide Perovskites for Thermoelectrics

“…A recent study systematically investigated the impacts of metal oxide layers on CsSnI 3 films. [ 71 ] The defect states of the metal oxide can trap the electrons from the perovskites, leading to the prompt formation of Sn 4+ , which subsequently increase the carrier density. A PF of 186.58 µW m −1 K −2 was reported at room temperature in CsSnI 3 /ZrO 2 bilayer, better than 148.61 µW m −1 K −2 of the pristine CsSnI 3 thin film.…”

Unlocking the potential of metal halide perovskite thermoelectrics through electrical doping: A critical review

“…(A) Timeline and progress in thermoelectric conversion efficiency represented for conventional inorganic 27–31,120–145 and organic thermoelectric materials, 32,146–157 as well as the emerging MHPs 21,22,51,54,67,74,158–162 . The gray dashed line represents the theoretical ZT range of MHPs, 33–36 and the gray dashed box in the bottom right corner indicates the experimental values obtained for MHPs.…”

“…Although organic materials, represented by poly(3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS), 32 have also been explored for thermoelectrics, their performance is F I G U R E 1 (A) Timeline and progress in thermoelectric conversion efficiency represented for conventional inorganic [27][28][29][30][31] and organic thermoelectric materials, 32,[146][147][148][149][150][151][152][153][154][155][156][157] as well as the emerging MHPs. 21,22,51,54,67,74,[158][159][160][161][162] The gray dashed line represents the theoretical ZT range of MHPs, [33][34][35][36] limited by their relatively low mobility, limiting their efficiency as thermoelectric generators. On the other hand, MHPs offer a promising alternative for thermoelectric applications due to their unique properties, combining the high mobility 24 of inorganic materials with the ultralow thermal conductivity [19][20][21] and facile processing 4,10,11,14 of organic materials (see Figure 1B), making them a strong ...…”