Solution‐processed perovskite quantum dots (QDs) are promising candidates for fabrication of semitransparent and tandem solar cells due to the bandgap tunability. In this work, cesium lead triiodide (CsPbI3) QDs are synthesized with a stable cubic phase and efficient perovskite solar cells (PSCs) are fabricated using the ligand exchange technique. Monolayer graphene is grown by chemical vapor deposition technique and a dry process to transfer graphene on top of the device is developed. Based on this approach, an efficient inverted PSC is demonstrated with a high average visible transmittance (AVT). After optimization, PSCs based on silver and graphene electrodes with power conversion efficiencies (PCEs) of 9.6% and 6.8% are achieved, respectively. Additionally, by tuning the thickness of the active layer, a PSC with PCE of 4.95% and AVT of 53% is demonstrated, indicating the potential of CsPbI3 QDs for the fabrication of semitransparent devices applicable in windows.

Large area graphene grown by chemical vapor deposition (CVD) has been the main focus of many researchers due to its vast areas of applications such as sensing or photovoltaics.Addressing the main challenges in transfer techniques such as Roll-to-Roll (R2R) process is a critical step for scaling up and commercialization of graphene. In this work, we employ a R2R transfer technique and improve the electrical properties of transferred graphene on flexible substrates using parylene as an interfacial layer. We deposit a layer of parylene on graphene/copper (Cu) foils grown by CVD and laminate them onto EVA/PET. Then, the samples are delaminated from the Cu using an electrochemical transfer process, resulting in flexible and conductive substrates with sheet resistance of below 300 Ω/sq, which is significantly better (4-fold) than the sample transferred by R2R without parylene (1200 Ω/sq). By scanning over different types of parylene (N, C, and D) here, we find that parylene C and D are better candidates than parylene N, given the higher conductivity measured on the as-transferred graphene samples. Our characterization results indicate that parylene C and D dope graphene due to the presence of chlorine atoms in their structure, resulting in higher carrier density and thus lower sheet resistance. Density functional theory (DFT) calculations reveal that the binding energy between parylene and graphene is stronger than that of EVA and graphene, which may lead to less tear in graphene during the R2R transfer. Finally, we fabricate organic solar cells (OSCs) on the ultrathin and flexible parylene/graphene substrates and achieve an ultra-lightweight device with a power conversion efficiency (PCE) of 5.86% comparable with PET/ITO ones, which has also a high power-per-weight of 6.46 W/g. In this study, we employ PV2000/PC 60 BM blend for the device fabrication, which does not require any encapsulation due to its superior air-stability.

Interface engineering by PFN-P2 and compositional engineering using water additive enable an efficient and stable perovskite solar cell with 20.5% efficiency.

Stability is the main challenge in the field of organic-inorganic perovskite solar cells (PSCs). Finding low-cost and stable hole transporting layer (HTL)is an effective strategy to address this issue. Here, a new donor polymer, poly(5,5-didecyl-5H-1,8-dithia-as-indacenone-alt-thieno[3,2-b]thiophene) (PDTITT), is synthesized and employed as an HTL in PSCs, which has a suitable band alignment with respect to the double-A cation perovskite film. Using PDTITT, the hole extraction in PSCs is greatly improved as compared to commonly used HTLs such as 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl) amino]-9,9′-spirobifluorene (spiro-OMeTAD), addressing the hysteresis issue. After careful optimization, an efficient PSC is achieved based on mesoscopic TiO 2 electron transporting layer with a maximum power conversion efficiency (PCE) of 18.42% based on PDTITT HTL, which is comparable with spiro-OMeTAD-based PSC (19.21%). Since spiro-based PSCs suffer from stability issue, the operational stability in the PSC with PDTITT HTL is studied. It is found that the device with PDTITT retains 88% of its initial PCE value after 200 h under illumination, which is better than the spiro-based PSC (54%).the stability is the main challenge in the PSCs, which is a key step for commercialization of these devices. [19][20][21] One of the main reasons for the instability of PSCs is the hole transporting layer (HTL) materials, which can be addressed properly by using new alternative HTLs. [22][23][24] One of the most commonly used HTLs in the PSCs is 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD), which is a great choice for the fabrication of highly efficient PSC over 23%. [5,25] However, the PSCs based on Spiro-OMeTAD suffer from poor stability due to the presence of unstable dopants as well as many voids through the HTL. In order to address this issue, compositional engineering by adding new additives into the molecular structure of spiro or interface engineering by adding an extra layer on top of the spiro could be potential solutions. [25][26][27][28][29] For example, Sunehira et al. [30] applied a thin layer of MoO 3 between spiro and electrode, resulting in an efficient PSC with better stability.These strategies improved the stability of the PSCs slightly and could not be an ideal solution for this issue. Consequently, replacement of spiro-OMeTAD using new stable HTLs is a better choice to improve the stability of the PSCs. There are many organic and inorganic HTLs for replacing spiro, however, they are expensive such as poly(triaryl amine) PTAA, require high-temperature annealing such NiO, or show limited efficiency and stability. [31][32][33][34][35] In this work, we synthesize a new and low-cost donor polymer, poly(5,5-didecyl-5H-1,8-dithia-as-indacenone-altthieno[3,2-b]thiophene) (PDTITT), and employ it as a potential HTL for the fabrication of efficient and stable PSCs. Our proposed polymer is cheaper than commonly used HTL polymers such as spiro and PTAA, thanks to its lower synthesis complexity, ...