Tensile Stress-Dependent Fracture Behavior and Its Influences on Photovoltaic Characteristics in Flexible PbS/CdS Thin-Film Solar Cells

Tensile stress-dependent fracture behavior of flexible PbS/CdS heterojunction thin-film solar cells on indium tin oxide-coated polyethylene terephthalate (PET) substrates is investigated in terms of the variations of fracture parameters with applied strains and their influences on photovoltaic properties. The PbS absorber layer that exhibits only mechanical cracks within the applied strain range from ∼0.67 to 1.33% is prepared by chemical bath deposition at different temperatures of 50, 70, and 90 °C. The PbS thin films prepared at 50 °C demonstrate better mechanical resistance against the applied bending strain with the highest crack initiating bending strain of ∼1.14% and the lowest saturated crack density of 0.036 μm^–1. Photovoltaic properties of the cells depend on the deposition temperature and the level of applied tensile stress. The values of short-circuit current density and fill factor are dramatically reduced above a certain level of applied strain, while open-circuit voltage is nearly maintained. The dependency of photovoltaic properties on the progress of fractures is understood as related to the reduced fracture energy and toughness, which is limitedly controllable by microstructural features of the absorber layer

Assessment of the risk of bias in included randomized controlled trials according to the revised version of Cochrane risk-of-bias tool for randomized trials.

In two studies, overall assessment was identified as low risk.</p

Forest plots of comparison of complete recovery rate of ellipsoid zone between the inverted internal limiting membrane flap and internal limiting membrane peeling groups.

Comparison of ellipsoidal zone recovery at (A) 3 months and (B) 6 months after surgery revealed no significant difference between the two groups. CL, confidence interval; ILM, internal limiting membrane; M–H, Mantel–Haenszel.</p

PRISMA 2009 checklist.

PurposeTo evaluate the efficacy of inverted internal limiting membrane (ILM) flap technique in full-thickness macular holes (MHs) with a size of ≤400 μm compared to the ILM peeling technique.MethodsRelated literatures that compared inverted ILM flap and ILM peeling in MHs ≤ 400 μm were reviewed by searching electronic databases including Pubmed, EMbase, ClinicalTrials.gov, and Cochrane Library up to April 2023. The primary outcome measure was hole closure rate, and the secondary outcome measures were the mean postoperative best-corrected visual acuity (BCVA), retinal sensitivity, and outer status of the retinal layers, including the external limiting membrane and ellipsoid zone. The quality of the articles was assessed according to the revised version of the Cochrane risk-of-bias tool for randomized trials or the Newcastle–Ottawa scale. In the case of heterogeneity, a sensitivity analysis was conducted, and publication bias was visually evaluated using a funnel plot.ResultsThis review included six studies with 610 eyes for the primary outcome and 385 eyes for the secondary outcomes, which were two randomized control trials and four retrospective studies. Pooled data revealed that the overall MH closure rate was 99.4% in the inverted ILM flap group and 96.2% in the ILM peeling group, without significant difference between the two groups (odds ratio = 3.91; 95% confidence interval, 0.82~18.69; P = 0.09). The inverted ILM flap technique did not have a favorable effect on the BCVA, retinal sensitivity, or recovery of the outer retinal layers. These results were consistent with those of the subgroup analysis of the different follow-up periods. No significant publication bias was observed.ConclusionIn eyes with MHs of ≤400 μm, both techniques demonstrated excellent surgical outcomes without significant differences. Therefore, surgical techniques can be selected according to surgeon preferences.</div

Forest plots of comparison of retinal sensitivity between the inverted internal limiting membrane flap and internal limiting membrane peeling groups.

No significant difference was observed between two groups. Owing to significant heterogeneity, a random-effects model was used. CL, confidence interval; ILM, internal limiting membrane; IV, inverse variance; SD, standard deviation.</p

Forest plots of comparison of complete recovery rate of external limiting membrane between the inverted internal limiting membrane flap and internal limiting membrane peeling groups.

(A) Comparison of external limiting membrane recovery after surgery and (B)–(D) the result of subgroup analysis based on follow-up duration. The follow-up duration was subdivided into (B) 3 months, (C) 6 months, and (D) 12 months after surgery, and no significant difference at each period was observed between the two groups. A random-effects model was used in the analysis in the 3-month and 12-month results since a significant heterogeneity was observed. CL, confidence interval; ILM, internal limiting membrane; M–H, Mantel–Haenszel.</p

Funnel plot for evaluating the publication bias.

(A) Macular hole closure rate; (B) preoperative best-corrected visual acuity (BCVA); (C) postoperative BCVA; (D) complete recovery rate of external limiting membrane. (A)–(D) Scattered points corresponding to the included studies were mostly distributed within the range of inverted funnel. (C) One point of study in postoperative BCVA was located slightly out of the inverted funnel. A relatively low publication bias could have influenced the results. OR, odds ratio; MD, mean difference; SE, standard error.</p

Forest plots of comparison of postoperative best-corrected visual acuity (BCVA) between the inverted internal limiting membrane flap and internal limiting membrane peeling groups.

(A) Forest plot of postoperative BCVA and (B)–(D) forest plots of postoperative BCVA based on the follow-up duration as the subgroup analysis. The subgroup analysis compared BCVA between two groups at (B) 3 months, (C) 6 months, and (D) 12 months postoperatively, respectively, and no differences were identified. A random-effects model was used in the analysis at 3 months and 6 months since significant heterogeneity was observed. CL, confidence interval; ILM, internal limiting membrane; IV, inverse variance; SD, standard deviation.</p

Characteristics of studies included in the meta-analysis: Baseline characteristics of the inverted internal limiting membrane flap and internal limiting membrane peeling groups.

Characteristics of studies included in the meta-analysis: Baseline characteristics of the inverted internal limiting membrane flap and internal limiting membrane peeling groups.</p

Quality assessment using the Newcastle–Ottawa scale for non-randomized controlled trial studies.

Quality assessment using the Newcastle–Ottawa scale for non-randomized controlled trial studies.</p