Thin-film PV modules are made by depositing a thin layer of semiconductor onto a low-cost substrate, rather than by cutting cells from silicon wafers. The main thin-film types are amorphous silicon (a-Si), cadmium telluride (CdTe) and copper indium (gallium) diselenide (CIGS or CIS), with active layers only a few micrometers thick or less. Thin-film modules usually cost less to make than crystalline silicon modules, but they are less efficient, so they need more land area and more balance-of-system material for the same power. Some thin-film modules are flexible, which allows mounting options such as solar covers on landfills. Others are rigid and can go on fixed-tilt or tracking structures. Thin-film cells are very sensitive to reverse bias, which is usually caused by shading. A shaded cell can form a shunt path that overheats at a single spot, and bypass diodes may not be able to protect the cells. Shunts from manufacturing defects or from hot-spot operation can be seen with electroluminescence imaging or lock-in thermography. There is much less field experience with thin-film modules than with crystalline silicon, and many failures are specific to one manufacturer. Some string inverter manuals list thin-film modules without grounding as allowed PV string types.
related_toc1 drafted · lead Crystalline silicon PV
PV cell technologies are grouped as crystalline or thin film; thin film costs less but is less efficient.
sec=2.3.3 h=278122ccbfb2sec=2.3.1 h=f7fb67df3e72sec=h62 h=c4ba2e7330fcc2 drafted · lead Cell reverse bias
Thin-film cells are very sensitive to reverse bias. Junction breakdown forms shunt paths that lead to hot spots.
sec=6.3.2 h=eeffb36464cec3 drafted · lead Partial shading
In thin-film modules, reverse bias is usually caused by shading.
sec=6.3.2 h=eeffb36464cec4 drafted · lead Module Hotspot from Cell Damage
Shunt hot spots heat a single point and can badly damage thin-film modules.
sec=6.3.2 h=eeffb36464cec5 drafted · lead Bypass diode
In thin-film modules, bypass diodes may not be usable to limit reverse voltage at affected cells.
sec=6.3.2 h=eeffb36464cec6 drafted · lead Electroluminescence imaging
EL imaging easily shows shunts in thin-film cells.
sec=6.3.2 h=eeffb36464cec7 drafted · lead IEC 61646 proposed
Hot-spot testing of thin-film modules is done in accordance with IEC 61646.
sec=6.3.2 h=eeffb36464cec8 drafted · lead Temperature coefficient
CdTe modules are described as having good low-light response and good temperature response coefficients.
sec=h62 h=c4ba2e7330fcefficiencyConditions: Overall efficiency of an amorphous silicon (a-Si) thin-film module, as reported in NREL landfill guidance
sec=3.2.1.2 h=aff70a9b72e8review note: possible conflict with c10 (same source; check the conditions); possible conflict with c11 (same source; check the conditions)conflicts with: Thin-film PV (c14)
c10 drafted · lead 11–14 PERCENT
Conditions: Overall efficiency of a CIGS thin-film module, as reported in NREL landfill guidance
sec=3.2.1.2 h=aff70a9b72e8review note: possible conflict with c9 (same source; check the conditions); possible conflict with c12 (same source; check the conditions)
c11 drafted · lead 11–12 PERCENT
Conditions: Overall efficiency of a CdTe thin-film module, as reported in NREL landfill guidance
sec=3.2.1.2 h=aff70a9b72e8review note: possible conflict with c9 (same source; check the conditions); possible conflict with c12 (same source; check the conditions)
Conditions: Amorphous silicon thin-film products (NREL landfill guidance, product section)
sec=5.4.3 h=878a98426819review note: possible conflict with c10 (same source; check the conditions); possible conflict with c11 (same source; check the conditions)conflicts with: Thin-film PV (c14)
c13 drafted · lead ≤ 12 PERCENT
Conditions: CdTe thin-film modules (NREL landfill guidance, product section)
sec=5.4.3 h=878a98426819Conditions: Typical efficiency of a CdTe thin-film module, given as an example in SMA leakage-capacitance guidance
sec=h8 h=052970e32ad1conflicts with: Thin-film PV (c9)conflicts with: Thin-film PV (c12)
related_to c6related_to c1related_to c6