The photodiode is a light-sensitive semiconductor diode that converts the light energy into voltage or current based on the mode of operation. In general, Photodiodes are operated in reverse bias condition.

a black coating is applied to the glass Photodiode to detect only IR rays. The photodiode allows the current to pass through it if the photodiode is exposed to IR rays and it doesn't allow current to pass through it if no IR rays fall on it. The amount of current passed through the photodiode is directly proportional to the amount of IR rays falls on it.

Size: 5mm.
Length: 37mm.
Lens Color: Black.
Emitted Colour: Infrared.
wavelength: 940nm.
Forward Voltage (V): 1.2-1.4V.
Forward Current (mA): 100mA.
Transmitting and receiving distance: about 7 - 8 M.

Arduino Scheme for making IR Communication between IR LED And IR Photodiode:

Arduino Code for making IR Communication between IR LED And IR Photodiode:

Arduino IR Transmitter Code:

void setup() {
  Serial.begin(9600);/* Define baud rate for serial communication */
}

void loop() {
  int count;
  for(count = 0; count<100; count++)
  {
    Serial.println(count);
    delay(1000);
  }
}

Arduino IR Receiver Code:

void setup() {
  Serial.begin(9600);/* Define baud rate for serial communication */
}

void loop() {
if(Serial.available())/* If data is available on serial port */
  {
    Serial.print(char(Serial.read()));/* Print character received on to the serial monitor */
  }
}