Developing PTB7-Th:ITIC based semi-transparent organic solar cells with pulsed laser deposited MoO3 as the hole transport layer

Ugwuanyi, Godwin ORCID: https://orcid.org/0000-0003-2871-0509 2023. Developing PTB7-Th:ITIC based semi-transparent organic solar cells with pulsed laser deposited MoO3 as the hole transport layer. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Solar cells are specialised diode, which can convert photon energy into electric energy by the photovoltaic effect. Semi-transparent organic solar cells (ST-OSCs) have the potential to contribute to clean energy and environment. One of the key drawbacks associated with ST-OSCs is the poor device performance, which limits their economic viability. This work explores the possibility of developing efficient PTB7-Th:ITIC based ST-OSCs by incorporating pulsed laser prepared MoO3 as their hole transport layer (HTL). The first stage of this study focused on systematic investigation to establish spin-coating speed and annealing temperature that enables fabrication of zinc oxide with desirable optical and morphological properties and offer an effective route to prepare the electron transport layer (ETL) for ST-OSCs. The second stage of the research centres on identifying suitable concentration of PTB7-Th:ITIC solutions for preparing the organic bulk-heterojunction (OBHJ) films with satisfactory optical and morphological characteristics as an effective photoactive layer. The samples fabricated with 0.0051 mol/dm3 concentration have estimated Eg of 1.53 eV, RMS of 0.52nm, and transparency colour of x = 0.312, y = 0.329, CCT = 5738 k, showing close colour to natural white light. The best performing STOSC exhibited a Voc, Jsc, FF, and PCE of 0.47 V, 37.25 mA/cm2 , 28.6%, and 5.1%, respectively. The third stage of the study focuses on exploiting the precise control of deposition parameters for accurate transfer of target stoichiometry to substrates using pulsed laser deposition (PLD), aiming at establishing suitable ablation energy to make MoO3 thin films with required optical and morphological characteristics. The samples prepared at 160 mJ exhibited a transmittance of 64.3% in the visible light region, Eg of 3.10 eV, transparency colour of x = 0.322, y = 0.326, and CCT = 5964, and RMS of 3.12 nm. At the final stage, J-V curves of ST-OSCs without and with MoO3 layers were characterised. The best performing ST-OSCs without MoO3 achieved a Voc, Jsc, FF, and PCE of 0.68 V, 10.84 mA/cm2 , 39.9%, and 3.0%, respectively. Whereas the best performing ST-OSCs incorporating MoO3 made at 160 mJ exhibited a Voc, Jsc, FF, and PCE of 0.57 V, 43.59 mA/cm2 , 28.7%, and 7.2%, respectively. A decrease in the series resistance was observed for all ablation energy, except for the lowest energy of 140 mJ, which was comparable to that of the devices without the MoO3 HTL. A small series resistance is beneficial to enhance the performance of the devices by reducing the internal resistive power loss. Unfortunately, this benefit is likely to be cancelled by a decrease in the shunt resistance. These observations indicates that the original plan to use the PLD prepared MoO3 layer as an effective HTL has not been achieved. Instead, it led to an unexpected discovery of substantially increased Jsc, which is interesting and potentially beneficial for developing high performance ST-OSCs.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Engineering
Uncontrolled Keywords:	1). Semi-transparent organic solar cells (ST-OSCs) 2). PTB7-Th:ITIC 3). MoO3 4). Pulse laser deposition (PLD) 5). Spin-coating 6). Annealing temperature
Date of First Compliant Deposit:	9 May 2024
Last Modified:	09 May 2024 15:50
URI:	https://orca.cardiff.ac.uk/id/eprint/168734

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