The emergence of perovskite solar cells (PSCs) recently has brought new hope to the solar cell industry due to their incredible improvement of the power conversion efficiency (PCE), which can now exceed 20.0% within seven years of tremendous research. The efficiency and stability of PSCs depend strongly on the morphology and type of materials selected as the electron transport layer (ETL) in the device. In this review, the functions of the ETL based on titania (TiO₂) in n–i–p architecture PSCs, including planar heterojunction and mesoporous-structured devices, are reviewed in terms of the device performance and stability. Studies found that the application of suitable fabrication techniques and manipulation of the nanostructural properties of TiO₂ are crucial factors in ameliorating the short-circuit current density, J_SC, and fill factor, FF, of PSCs. On top of that, the effect of substituting TiO₂ with other potential inorganic materials like zinc oxide (ZnO), tin oxide (SnO₂), ternary metal oxides, and metal sulphides, as well as organic semiconductors including fullerene, graphene, and ionic liquids, towards the photovoltaic properties and stability of the devices are also elaborated and discussed. Meanwhile, the utilization of non-electron transport layers (non-ETLs), such as alumina (Al₂O₃) and zirconia (ZrO₂), as the mesoporous scaffold in PSCs is found to enhance the open-circuit voltage, V_OC, of the devices.

Sustainability has been greatly impacted by the reality of budgets and available resources as a targeted range of carbon emission reduction greatly increases due to climate change. This study analyses the technical and economic feasibility for three types of solar photovoltaic (PV) renewable energy (RE) systems; (i) solar stand-alone, a non-grid-connected building rooftop-mounted structure, (ii) solar rooftop, a grid-connected building rooftop-mounted structure, (iii) solar farm, a grid-connected land-mounted structure in three tropical climate regions. Technical scientific and economic tools, including life cycle assessment (LCA) and life cycle cost assessment (LCCA) with an integrated framework from a Malaysian case study were applied to similar climatic regions, Thailand, and Indonesia. The short-term, future scaled-up scenario was defined using a proxy technology and estimated data. Environmental locations for this scenario were identified, the environmental impacts were compared, and the techno-economic output were analysed. The scope of this study is cradle-to-grave. Levelised cost of energy (LCOE) was greatly affected due to PV performance degradation rate, especially the critical shading issues for large-scale installations. Despite the land use impact, increased CO₂ emissions accumulate over time with regard to energy mix of the country, which requires the need for long-term procurement of both carbon and investment return. With regards to profitably, grid-connected roof-mounted systems achieve the lowest LCOE as compared to other types of installation, ranging from 0.0491 USD/kWh to 0.0605 USD/kWh under a 6% discounted rate. A simple payback (SPB) time between 7–10 years on average depends on annual power generated by the system with estimated energy payback of 0.40–0.55 years for common polycrystalline photovoltaic technology. Thus, maintaining the whole system by ensuring a low degradation rate of 0.2% over a long period of time is essential to generate benefits for both investors and the environment. Emerging technologies are progressing at an exponential rate in order to fill the gap of establishing renewable energy as an attractive business plan. Life cycle assessment is considered an excellent tool to assess the environmental impact of renewable energy.

Perovskite solar cells (PSCs) have shown a significant increase in power conversion efficiency (PCE) under laboratory circumstances from 2006 to the present, rising from 3.8% to an astonishing 25%. This scientific breakthrough corresponds to the changing energy situation and rising industrial potential. The flexible perovskite solar cell (FPSC), which capitalizes on the benefits of perovskite thin-film deposition and operates at low temperatures, is key to this transition. The FPSC is strategically important for large-scale deployment and mass manufacturing, especially when combined with the benefits of perovskite thin-film deposition under moderate thermodynamic conditions. Its versatility is demonstrated by the ease with which it may be folded, rolled, or coiled over flexible substrates, allowing for efficient transportation. Notably, FPSCs outperform traditional solar panels in terms of adaptability. FPSCs have several advantages over rigid substrates, including mobility, lightweight properties that help transportation, scalability via roll-to-roll (R2R) deposition, and incorporation into textiles and architecture. This in-depth examination dives into their fundamental design and various fabrication techniques, which include conducting substrates, absorber layers, coordinated charge movement, and conductive electrodes. This review evaluates critical FPSC fabrication techniques such as thermal evaporation, R2R approaches, slot die and spray deposition, blade coating, and spin coating. The present challenges in constructing FPSCs with high performance and long-term stability are also highlighted. Finally, the solar industry's potential uses for both indoor and outdoor FPSCs have been discussed.

High-performance perovskite solar cells have attracted increased attention for photovoltaic applications and potentially replacing the predecessor generations. Nevertheless, the stability issues and the lead content has always been among the major concerns that barriers perovskite solar cells from commercialization. This review presents the discussion towards the inherent instability of perovskite solar cells and the development towards replacing lead with discussion towards their performance and challenges. The degradation of perovskite active layer would release toxic substance into the environment. The development towards low-toxic, lead-free and efficient perovskite solar cells is the key for a sustainable solar energy generation with the application of perovskite solar cells.