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A study on the inorganic-organic hybrids based on silicon-polymers and perovskite materials for energy and environment applications

A study on the inorganic-organic hybrids based on silicon-polymers and perovskite materials for energy and environment applications
Abdul Sami Rajput
Professor Jung Ho Lee
Issue Date
Hybrid solar cells (HSCs) based on inorganic semiconductors and organic conducting polymers syndicate the advantages of conventional PV and organic PV technologies to fabricate high conversion efficiency (CE) devices. Particularly, the hybrids using poly(3,4-ethylenedioxy-thiophene)-poly(styrene sulfonate) (PEDOT:PSS) and n-silicon nanowires (n-SiNWs) provide heterojunctions with the potential of light trapping, cost effectiveness, and high efficiency. However, the lack of control over passivation inside NWs results in intermittent junctions and recombination losses, which hamper built-in potential (Vbi) and conversion efficiency (CE). Here, we present a record CE of 13.5% by utilizing a near-zero reflecting device with radial core shell heterojunction between the hierarchy of black pyramidal Si (BPS) and bilayer PEDOT:PSS (Pp+). The ultraviolet-ozone (UV/O3) assisted very thin (~1.2 nm) tunneling oxide of SiO2 offers passivated interface for hybrid engineering. Our novel devices induce inversion with high Vbi of 0.71 eV, optimize the bilayer emitter contact by hole selectivity, and suppress density of interface surface states (Dit). The surface and bulk carrier life times are improved due to charge trapping and field-effective passivation by the Pp+ emitter. Furthermore, electric field distributions by finite-difference time-domain revealed the distinguishing features of photon trapping and carrier generation ability within BPS–Pp+ devices. Perovskite inorganic-organic solar cells are fabricated as sandwich structure of mesostructured TiO2 as ETMs, CH3NH3PbI3 as absorber material layer (AML), and spiro-Ometad as hole transport layer (HTL). The crystallinity, structural morphology, and thickness of TiO2 layer play a crucial role to improve the overall device performance. The randomly distributed one dimensional (1D) TiO2 nanowires (TNWs) provide excellent light trapping with open voids for active filling of visible light absorber compare to bulk TiO2. The organometal halide perovskite CH3NH3PbI3 possesses low-carrier diffusion length (100nm) compared to CH3NH3PbI3-xClx (1~2um) which hinder collection of free charges at the anode. Solid state photovoltaic device based on randomly distributed TNWs and CH3NH3PbI3 is fabricated with high Voc of 0.9 V, with CE of 6.44%. Mott-Schottky analysis lead to very high Vbi of 0.96 eV which indicate that there is no depletion layer voltage modulation in the perovskite solar cells fabricated with TNWs. Also, FDTD analysis reveal that the larger fraction of photo-generated charges are generated due to field convergence and guided modes at the interface of TNWs/CH3NH3PbI3 compared to bulk TiO2.
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