: When light is absorbed, it creates a bound electron-hole pair called an . Because of high binding energies (
In a silicon crystal, electrons move like waves through a perfect lattice. In organic films, which are often amorphous or disordered, charges must from one molecule to the next. This movement is often assisted by polarons —quasiparticles formed when a charge carrier deforms the surrounding molecular structure, "trapping" itself until it gains enough thermal energy to move. 4. Excitons: The Inseparable Pairs Introduction to the physics of organic semiconductors
The unique electronic properties of organic semiconductors originate from carbon hybridization and the formation of conjugated -electron systems. Carbon Hybridization and Conjugation physics of organic semiconductors pdf
Because organic solids lack long-range order, charge carriers cannot move freely like in silicon. Instead, they hop from one localized state to another via tunneling or thermally activated jumps. This leads to low mobility (often (10^-6) to (1 \text cm^2/\textVs)), which is a key challenge. The mobility strongly depends on temperature, electric field, and molecular packing.
Excellent for understanding molecular orbital theory. : When light is absorbed, it creates a
. Carriers jump between localized states because the materials are often disordered or amorphous. Light absorption in these materials creates
Instead of traditional valence and conduction bands, we talk about HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital). The energy difference between them typically falls between , allowing them to absorb and emit visible light. 2. How Charges Move: "The Hopping Mechanism" The mobility strongly depends on temperature
Typically 0.1 eV to 1.0 eV (much greater than thermal energy at room temperature,