The conversion of solar energy into usable electricity via a solid-state pn-junction-based photovoltaic (PV) device holds great opportunities in our quest to reduce our current dependence on fossil fuels and subsequently reduce harmful greenhouse gas emissions (Najm et al. 2021; Zhuk et al. 2017). Currently, global PV installations consist of monocrystalline silicon (c-Si), polycrystalline silicon (mc-Si), and thin-film technologies (Gulkowski, Zdyb, and Dragan 2019). The real trend in solar cell technology has to do with multicomponent thin film materials, which are believed to replace expensive crystalline silicon cell technology. Research has focused on identifying and improving the optimum light absorber, buffer and window layers (Islam and Thakur 2020; Vigil-Galán et al. 2015).
Cadmium sulfide (CdS) is an important II-VI compound semiconductor with high transparency, direct band gap transition (Eg~2.4 eV), high electron affinity (4.2 eV) and n-type conductivity (Horoz and Sahin 2017; Rajendra and Kekuda 2012). CdS also improves lattice heterojunction interface coupling, extends excess carrier lifetime, and optimizes band alignment of devices in which it is used. CdS thin films are considered as one of the most important materials for solar cell applications. It has a wide band gap with high optical transmittance and high electrical conductivity. For these reasons, it can be used as a window layer alongside other semiconductors such as CdS (Liu, Qiao, et al. 2020), CdTe (Bosio, Pasini, and Romeo 2020), CIGS (Ahmadpanah, Orouji, and Gharibshahian 2021) and ZnO (Liu, Luan, et al. 2020).
As a derivative of dye-sensitized solar cells, semiconductor-based solar cells attract extensive research due to their low cost effectiveness and ease of manufacture. Compared with conventional organic dyes, semiconductor materials offer some attractive advantages as light absorbers, including high molar extinction coefficient, tunable bandgap, large intrinsic dipole moment, and hot electron injection. In particular, the multi-exciton generation effect of semiconductor materials pushes the theoretical maximum power conversion efficiency of semiconductor-based solar cells up to 44%, which exceeds the Shockley and Queisser limit for conventional semiconductor solar cells (Goodwin et al. 2018). So far, various semiconductor materials such as CdS (Lee et al. 2017), CdSe (Horoz et al. 2012), PbS (Huang and Zou 2015), and CdTe (Li et al. 2020) have been used as sensitizers to build semiconductor-based solar cells. However, due to the limited light absorption capacity or incomplete charge separation, all power conversion efficiencies are much lower than the maximum theoretical value.
Activated carbon (AC) is a promising carbonaceous material with superior properties such as high porosity and internal surface area (Ece et al. 2020; Kutluay, Ece, and Şahin 2020; Şahin et al. 2021). Chemical and physical activation methods of AC allow materials to produce a controlled pore distribution and surface area that defines the electrode/electrolyte interface for photovoltaic applications (solar cells) (Arbab et al. 2016; Vispute et al. 2011). AC is incorporated into the electrodes of photovoltaic devices as follows: electroconductive additives, supports for active materials, electron transfer catalysts, intercalation hosts, and substrates for current leads. For these reasons, AC is of course also very suitable as electrode materials for solar cells (Mehmood et al. 2016).
In a CdS-based solar cell, CdS semiconductor materials play a very important role as sensitizers. It is of great importance to increase the photovoltaic efficiency of CdS-based solar cells, which are widely used in photovoltaic applications, with AC support (Shao et al. 2019). Also, AC is included in the electrodes of photovoltaic devices as electro-conductive additives, support for active materials. For these reasons, AC is used to improve efficiency in solar cells. In a related study, it was observed that the efficiency of the solar cell cell designed in the absence of AC was 3.38%, while the efficiency of the same solar cell cell with AC support was 5.45%. This result shows that the use of AC as a support material in photovoltaic applications has a great impact (Mehmood et al. 2016).
To the authors' knowledge, there is no known production of Mo-doped AC (defatted black cumin (Nigella Sativa L.) waste biomass-based) supported CdS semiconductor materials, and this presents an innovation aspect of our proposed study. Here, instead of undoped-doped CdS, which is frequently used in the literature, AC-doped CdS (CdS/AC) (5%, 10% and 15% by weight) and molybdenum (Mo)-doped with different concentrations (0.33%, 1% and 3% by weight) CdS/AC semiconductor materials are produced. The main purpose of the study is to determine how the incident photon-to‐current conversion efficiency (IPCE) of undoped and Mo-doped AC supported CdS semiconductor-based solar cell structures change and to interpret the observed effect in the light of the literature.